ISSN:1064-119X    

DOI:10.1080/10641199709379937

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A laboratory investigation of the geotechnical properties of a marine clay saturated with a series of monovalent, divalent, and trivalent cations revealed large differences in behavior which depend on the exchangeable cations. The exchangeable cations employed in this study are sodium (Na), potassium (K), ammonium (NH4), magnesium (Mg), calcium (Ca), and aluminum (Al) in order of increasing valency. An increase in the valency of the adsorbed cations leads to an improvement in the geotechnical properties of the marine clay, while for a constant valency an increase in the hydrated radius of the adsorbed cations results in a lower rate of consolidation. Analysis of the results show that geotechnical properties are improved for the marine clay with cations having higher valency and smaller hydrated ionic radius in the adsorbed complex. The beneficial changes in properties can be attributed to the improvement in the efficiency of flocculation as the valency of the adsorbed cations increases and the hydrated ionic radius decreases.

ISSN:1064-119X    

DOI:10.1080/10641199709379938

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

In the field of ocean engineering, a beginning has been made in the use of large‐sized suction anchors for safe anchoring of large compliant structures. Suction anchors derive most of their uplift resistance from passive suction developed during the pullout movement. This article describes a set of laboratory tests on model suction anchors of three different embedment ratios to estimate the pullout behavior of suction anchors in soft clays typical of Indian marine clays. Tests were conducted on model anchors installed in soil beds prepared at four different consistencies in a test tank. This study shows the influence of soil consistency and embedment ratio (L/D) on the pullout behavior of suction anchors and on the variation of suction pressure at the top of the soil plug. The test results reveal that the behavior of suction anchors is much better than the behavior of open‐ended anchors from the considerations of both capacity and deformation. The consistent development of suction inside the anchor top confirms the plug formation and significant breakout resistance in the form of suction‐induced reversed end bearing. The results are further analyzed in terms of suction breakout factors. Further, the effect of burial depth of suction anchor on pullout behavior is shown.

ISSN:1064-119X    

DOI:10.1080/10641199709379939

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The article is devoted to the problem of the dumping of suspended matter from Kaliningrad Amber Mining Plant to the Baltic Sea. Estimation of environmentally harmful pulp discharge is based on the requirements of the Russian State Service for Nature Protection (RSSNP) for maximum limited concentration of suspension in sewage waters, using the formula Cmax=N(Ct— Cb) + Cb, but taking into consideration the separate fractions in both surface and subsurface waters, where Ctis the concentration at the test site, Cbis the background concentration at the point of discharge, and N is the total dilution factor between the two sites. Field study results were the input data for maximum limited and actual discharges’ calculations and were based on 71 samples that showed wide variances of suspension concentrations for the internal background site of from 5.8 to 62.6 mg/L, and for the external background site of from 2.9 to 27.2 mg/L. The fluctuations are explained by variation in wind velocities which strongly influence the swell in the coastal area, causing sediment resuspension. On the basis of the experimental data, it is possible to plot an analytical relationship between values of N and wind velocities. Samples were analyzed for grain size and content of Fe, Mn, Cu, and Zn. It is concluded that the Kaliningrad Amber Mining Plant is the source of large amounts of dispersed fine terrigenous sediments and of occurrences of trace metals associated with them and, taking into account real conditions of wind velocities and flows in the coastal zone of the sea, the study has resulted in a useful basis for more detailed investigations of the anthropogenic influence on the ecological system of the southeast Baltic.

ISSN:1064-119X    

DOI:10.1080/10641199709379940

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A widespread distribution of hydrothermal and hydrogenetic manganese deposits is described in the results of the Hakurei‐Maru cruises conducted in the Bonin Arc areas of the West Pacific from 1984 to 1989. Manganese deposits occur in the active volcano chains, back‐arc basins, remnant back‐arc ridges, and oceanic seamounts.

ISSN:1064-119X    

DOI:10.1080/10641199709379941

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Erosion of sandy beaches is a worldwide problem that elicits innovative geoengineer‐ing techniques to reduce adverse impacts of shoreline retreat. Beach replenishment has emerged as the “soft”; shore‐stabilization technique of choice for mitigating beach erosion. This method of shore protection involves the addition of sand to the littoral sediment budget for sacrificial purposes. Because inland sand sources are often uneconomical or impractical to use, and known nearshore sources are limited, finding adequate quantities of suitable sand on the inner continental shelf is often vital to beach replenishment projects. The technical studies of survey and materials analysis that identify and delineate usable sand sources are sometimes almost as expensive as small‐project dredging, pumping, and placing the sand on the beach as fill. Inadequate quantity or substandard quality of shelf sand, as well as often‐prohibitive overhead expenses, thus compel shoreline managers to seek suitable sand sources offshore.

ISSN:1064-119X    

DOI:10.1080/10641199709379942

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Manganese crusts were recovered from Enarete and Palinuro Seamounts in the Tyrrhenian Sea. The crusts consist of porous, black, layered Mn oxides up to 45 mm thick. In some cases, the surface has a black metallic sheen similar to that observed in crusts from the Tonga‐Kermadec Arc. The crusts overlie substrates such as calcareous sediment, siltstone, and oyster shells. They consist dominantly of 10‐Å manganate and 7‐Å manganate, with minor quartz, calcite, aragonite, illite, mont‐morillonite, plagioclase, and goethite. The sample having the highest Mn content contained 52.8% Mn, 0.15% Fe, 46 ppm Ni, 84 ppm Cu, 26 ppm Zn, 6 ppm Pb, and 2,130 ppm Ba, with a Mn/Fe ratio of 347. It also had a low rare‐earth element (REE) abundance (La 2.7 ppm) and a negative Ce anomaly (Ce/La ratio 0.5). A TV profile on Palinuro showed the occurrence of yellow (Fe oxyhydroxide or nontronite), black (Mn oxide), and white (sulfate) halos in the sediment and opaqueness in the overlying water. Nontronite and massive sulfides were also recovered at some locations on Palinuro. The morphology, mineralogy, and composition of these crusts as well as ancillary geological evidence confirm that the crusts are of hydrothermal origin. Similar crusts occur in a number of island‐arc environments, particularly in the Pacific, and are known to be formed by low‐temperature hydrothermal venting. The origin of the Tyrrhenian Sea is complex but it is believed to be a back‐arc basin formed above a NW‐dipping subduction zone. The Aeolian islands and seamounts consist of 16 volcanic edifices which form an anticlockwise arc around the Marsili abyssal plain. Palinuro is the youngest of these. Our data support the idea that the Mn deposits formed as a result of submarine hydrothermal activity associated with subduction‐related processes.

ISSN:1064-119X    

DOI:10.1080/10641199709379943

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:1064-119X    

DOI:10.1080/10641199709379936

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor